Windings for electric machines such as asynchronous motors can be manufactured by means of the threading technique. In the manufacture of windings for electric machines, the threading technique is used for low-voltage motors operated at voltages below 50 V and in electric motors operated with higher voltages. When manufacturing windings for low-voltage motors (operating voltage=to 50 V), the windings are manufactured out of parallel wires in order to assure the required winding cross section.
Low-voltage motors that are operated with operating voltages below 50 V are used in steering motors for vehicles or for actuators used in vehicles. Electrical systems in motor vehicles today are generally designed as 12 V electrical systems; judging from current development trends, the use of 42 V electrical systems in motor vehicles could conceivably become the new standard. Both electrical system voltages, i.e. an electrical system voltage of 12 V and an electrical system voltage of 42 V, permit the use of low-voltage motors embodied in the form of asynchronous motors, which can be operated with an operating voltage of=50 V. The windings of low-voltage motors are produced from parallel wires in order to assure the winding cross section that these electric machines require. But producing windings for low-voltage motors, e.g. asynchronous motors, out of parallel individual wires results in a high degree of wiring complexity at the ends of the winding, which is generally manufactured by hand.
The windings for asynchronous motors manufactured out of parallel wires using the threading technique also have the disadvantage that the threading technique permits only a low slot space factor to be achieved. Because of the low level of utilization of the slots into which the parallel wires are inserted, in order to achieve sufficient winding cross sections, a larger number of slots are required, which in turn requires a large structural volume in electrical machines that can be operated in the low-voltage range below 50 V, for example of the kind represented by asynchronous motors used as steering motors.
When manufacturing DC motors, it is also known to use the plugging technique to manufacture winding cores.
According to the threading technique, see “Technologie des Elektromaschinenbau's” [Technology of Electric Machine Engineering] by R. Tzscheutschler, H. Olbrich, and W. Jordan, Verlag Technik GmbH, Berlin, p. 336, Technological Principles For Manufacturing Windings, loose prewound coils of enameled copper wire are inserted into half-closed slots. The threading process is used to wind stators. Depending on the stroke speed of a hydraulic cylinder and the stator core length, a coil side, a coil, or even an entire winding can be threaded in a slot-filling manner; it is also possible to insert cover insulating caps at the same time. The fundamental principle is based on the fact that the coil sides are narrowed to less than the slot width and protected from the slot edges in order to be threaded into the slots through the exertion of force on the front end by means of a stroke motion. The alignment of the wires and the protection from the slot edges can be achieved by means of polished steel profiles that are also referred to as threading needles. In the threading tool, the threading needles are adapted to a particular stator plate cut and to the core length. The coils are wound or suspended in accordance with the winding scheme.
At the end of the threading process, it is typical for the layer of threaded coils to be S-shaped in the longitudinal section of the stator. In addition, the coils often are not centered in relation to the stator. At the point at which they emerge, the coil ends bridge over the bore space in a sinuous fashion, which occurs to a particularly pronounced degree in bipolar windings. Additional threading procedures thus require intermediate shaping operations.
The threading method can be used to produce 1-phase 2-phase, and 3-phase windings with an arbitrary number of poles. Preferably, they are embodied in the form of single-layer windings with flat arrangements of the winding heads. Two-layer windings can be produced in two threading steps; a covering cap profile should be used for intermediate insulation.